DE3325372A1 - METHOD FOR THE PRODUCTION OF PURE ADIPINO ACID MONOESTERS - Google Patents

Description

BASF Aktiengesellschaft * "** O.Z. 0050/36619

Process for the preparation of pure adipic acid monoesters

In the previously known processes for the preparation of adipic acid monoesters one starts from adipic acid and tries to interrupt the esterification at the monoester stage. According to that known from US Pat. No. 4,314,071 Process esterifies adipic acid with alcohols in aqueous solution in the presence of sulfuric acid as a catalyst, the monoester in to the extent that it arises, it is extracted immediately with non-polar solvents. The implementation will be carried out within 5 days, which involves a considerable expenditure of time. In addition, adipic acid monoesters are only obtained from the extract with a purity of 96%, while it takes a complicated work-up to get purer Adipic acid monoester to arrive.

Even after the method described in DE-OS 24 04 359 one starts from Adipic acid and esterifies it with alcohols in the presence of at least one mole of water per mole of adipic acid .. The yields of adipic acid monoester leave something to be desired, since considerable amounts of adipic acid diester are obtained as a by-product. The latter have to take a lot of effort are separated in order to obtain pure adipic acid monoester.

It was therefore the technical task to convert adipic acid monoesters in high yield and high purity.

This technical problem is solved in a method for production of pure adipic acid monoesters, whereby one

a) Pentenoic acid ester with carbon monoxide and hydrogen at one temperature from 90 to 140 ° C under a pressure of 5 to 300 bar in the presence of carbonyl complexes of cobalt or rhodium and 5-formylvaleric acid ester separates and

b oxidizing the thus obtained 5-formylvaleric ester with molecular oxygen or a gas containing this, at a temperature of 20 to 100 ⁰ C under a pressure of 1 to 10 bar).

The new process has the advantage that it proceeds with high yields and leads to adipic acid monoester with a purity of> 99%.

The starting compound used is pentenoic acid esters, e.g. alkyl esters with 1 to 12 carbon atoms, cycloalkyl esters with 5 to 12 carbon atoms, Alkaryl esters with 7 to 9 carbon atoms or phenyl esters. It is preferred to start from alkyl pentenoates, in particular those

BASF Aktiengesellschaft * "* ^ J? ** - " - "* - * OZ 0050/36619

-1-

derived from alkanols with 1 to 4 carbon atoms. Advantageous 4 and / or 3 pentenoates are used. Suitable pentenoates are, for example, 4-pentenoic acid methyl ester, 4-pentenoic acid ethyl ester, Propyl 3-pentenoate, butyl 3-pentenoate, octyl 4-pentenoate, S-pentenoic acid cyclohexyl ester, 4-pentenoic acid benzyl ester or 3-pentenoic acid phenyl ester "

A mixture of carbon monoxide and hydrogen is used for the reaction. The mixture advantageously contains carbon monoxide and hydrogen in a molar ratio of 10:90 to 50:50. In particular, there is a mixture Proven in a molar ratio of carbon monoxide to hydrogen of 10:40.

In the hydroformylation of a temperature of 90 to 140 ° C and applies to the use of rhodium carbonyl complex, a temperature advantageously of 100 to 120 ⁰ C. Furthermore, a pressure of 5 to 300 bar is maintained, and if rhodium carbonyl complexes are used, a pressure of 5 to 20 bar is advantageous.

The hydroformylation catalysts used are carbonyl complexes des Rhodium or cobalt. The carbonyl complexes can be prepared prior to the reaction are or are advantageously formed in situ from salts of rhodium or cobalt, e.g. their fatty acid salts such as cobalt acetate or rhodium acetate. The rhodium or cobalt carbonyl complexes are also advantageous modified by tertiary phosphines or tertiary phosphites. For example, tertiary alkyl and aryl phosphines and tertiary ones are suitable Alkyl and aryl phosphites. It is preferred to use substituted triphenylphosphine Triarylphosphines such as tritolylphosphine, alkyldiarylphosphines such as hexyldiphenylphosphine.

The rhodium concentration is advantageously 50 to 500 ppm, based on the reaction mixture calculated as the metal. The modification of the carbonyl complexes of rhodium with the phosphines or phosphites mentioned has proven particularly useful. It is advantageous to use phosphines or Phosphites in a 3 to 100-fold molar excess, based on rhodium.

If cobalt carbon catalysts are used, modification by phosphines and phosphites can be dispensed with, especially if 3-pentenoic esters are used for the hydroformylation, such as are obtained, for example, directly in the reaction of butadiene with carbon monoxide and alkanols in the presence of cobalt carbonyl complexes. Reaction mixtures thus obtained are hydroformylated advantageous bar with a cobalt carbonyl catalyst without further additives at a temperature of 100 to 140 ⁰ C and under a pressure of 150 to 200 micrometers.

BASF Aktiengesellschaft -A - OZ 0050/36619

It is also possible to use solvents such as liquid aromatic ones Hydrocarbons e.g. toluene or xylene, also carboxylic acid esters such as acetic acid, butyric acid or valeric acid esters as well as high-boiling ones Condensation products as they arise in the reaction itself.

The reaction mixture obtained in the hydroformylation of the pentene esters contains, in addition to unreacted pentenoic esters, the catalysts used, the 5-formylvaleric acid ester produced as a product of value as well as by-products such as 4-foraylvaleric acid ester, valeric acid ester, Hydroxycaproic acid esters and high-boiling condensation products. From these reaction mixtures, the reaction products are first removed from the catalyst e.g. separated by distillation or extraction and then isolated by fractional distillation. The 5-fromylvaleric acid ester thus obtained is used for the oxidation in the second stage.

The oxidation of the 5-formylvalerate is carried out at a temperature of 20 to 100 ⁰ C and under a pressure of 1 to 10 bar contained with molecular oxygen or molecular oxygen gases. Advantageously, a temperature of 50 to 8O ⁰ C to obtain a case. The gases containing molecular oxygen can contain, for example, up to 80% by volume of inerts such as nitrogen, carbon dioxide or noble gases. The oxidation usually takes place without a catalyst. However, it can also be achieved by adding catalysts such as alkali hydroxides, e.g. potassium hydroxide or sodium hydroxide in amounts of 0.001 to 0.5% by weight or metal salts of cobalt or manganese, e.g. cobalt acetate or manganese acetate in amounts of 0.001 to 0.1% by weight, preferably 0.02 to 0.08% by weight, calculated as metal, are additionally accelerated.

By distilling the reaction mixture obtained in this way, adipic acid monoesters are obtained, which is free from diester and adipic acid and does not contain any high-boiling components.

Adipic acid monoesters obtainable by the process of the invention are suitable for the production of sebacic acid esters after Kolbe synthesis.

The method according to the invention is illustrated by the following example.

example

In a high-pressure vessel with a capacity of 2 liters, 360 g of a methyl pentenoate mixture, which contains 342 g (3 mol) of methyl 4-pentenoate,

BASF Aktiengesellschaft Ά ~ OZ 0050/36619

- £ - 332S372

dissolved in 600 ml of toluene. 70.2 g (268 mmol) of triphenylphosphine and 108 mg (1.04 mmol) of rhodium in the form of the complex compound HRhCOLß (L = triphenylphosphine) are added as a catalyst. The reaction mixture is ^{heated to 110 °} C. and then adjusted to a pressure of 8 bar with a mixture of 80% by volume of hydrogen and 20% by volume of carbon monoxide. If the pressure falls below 7 bar during the reaction, it is adjusted back to 8 bar by forcing an equimolecular mixture of hydrogen and carbon monoxide. After a reaction time of 2 hours, the reaction is terminated and the reaction mixture is worked up by distillation. Here one obtains

unreacted methyl pentenoate 81.3 g (18.5%)

Methyl valerate 9.1 g (2.6%)

4-formylvaleric acid methyl ester 26.8 g (6.2%)

5-formylvaleric acid methyl ester 310.2 g (71.8%)

Hydroxycaproic acid methyl ester 2.2 g (0.5 X)

High-boiling condensation products 1.7 g (0.4%)

The hydroformylation yield is 71.8% and the selectivity to 5-formylvalerian ester is 88.1. % »

288 g (2 mol) of the methyl 5-formylvalerate obtained above are oxidized in a bubble acid for 6 h at normal pressure (1 bar) and at a temperature of 50 ^° C. by introducing oxygen. A conversion of > 99% is achieved. The reaction mixture obtained is distilled in a packed column at 2 mbar and a temperature of 126.degree. This gives 307 g Adipinsäuremonoraethylester in a purity of> 99 Z. The yield of the oxidation is 95.9%.

Claims (1)

BASF Aktiengesellschaft 0.Z. 0050/36619 Claims Process for the preparation of pure adipic acid monoesters, characterized in that 05 a) pentenoates with carbon monoxide and hydrogen at a temperature of 90 to 14O ⁰ C under a pressure of 5 to 300 bar in the presence of carbonyl complexes of cobalt or rhodium and separates 5-formylvaleric ester and b) the thus obtained 5-formylvaleric acid ester with molecular Oxygen or such gases contained at a temperature of 20 to 100 ⁰ C under a pressure of 1 to 10 bar oxidized. 15 2. The method according to claim 1, characterized in that 3- and / or 4-pentenoic acid Cj- to C ^ alkyl ester is used. 3. The method according to claims 1 and 2, characterized in that rhodium carbonyl complexes with tertiary phosphines or ter- 20 modified tiary phosphites are used as catalysts. 4. Process according to Claims 1 to 3, characterized in that 3-pentenoates are reacted in the presence of cobalt carbonyl complexes. 329/83 Bk / Kl 13.07.83